Internet Engineering Task Force (IETF) RFC4861 specifies the Neighbor Discovery Protocol (NDP) for IPv6. IPv6 nodes on the same link use NDP to discover each other's presence, to determine each other's link-layer addresses, to find routers, and to maintain reachability information about the paths to active neighbors. IETF RFC826 specifies the Address Resolution Protocol (ARP), which finds an analogous use to NDP but with respect to link-layer address discovery for IPv4 nodes.
Virtual Leased Line (VLL) is a service for providing Ethernet based point to point communication over Internet Protocol (IP) and Multi Protocol Label Switching (MPLS) networks (IP/MPLS). This technology is also referred to as Virtual Private Wire Service (VPWS) or Ethernet over MPLS (EoMPLS). The VPWS service provides a point-to-point connection between two Customer Edge (CE) devices. It does so by binding two attachment circuits (AC) to a pseudowire that connects two Provider Edge (PE) devices, wherein each PE device is connected to one of the CE devices via one of the attachment circuits. VLL typically uses pseudowire encapsulation for transporting Ethernet traffic over an MPLS tunnel across an IP/MPLS backbone. More information on pseudowires can be found in “Pseudo Wire Emulation Edge-to-Edge (PWE3) Architecture”, RFC3985, IETF, March 2005, by S. Bryant and P. Pate. When the VLL connects CE devices with dissimilar AC protocols over an IP/MPLS network, it is referred to as an IP interworking VLL.
IETF Draft “draft-ietf-l2vpn-arp-mediation-09” specifies ARP mediation for IP Interworking VLLs. ARP mediation is used when the aforementioned attachment circuits are of different link layer technologies and payloads of the frames carried over the pseudowire consist solely of IP datagrams. ARP mediation refers to the process of resolving link layer addresses when dissimilar resolution protocols are used on the attachment circuits. Part of ARP mediation requires that the IP address of a CE device's AC interface is communicated to the PE device at the far-end of the pseudowire. This is done so that a PE device can act as an ARP proxy for its locally attached CE device. An LDP control link of the pseudowire is used to exchange these IP addresses between the PE devices.
Similar to ARP mediation for IP interworking VLLs in IPv4 networks, in order to support IP interworking VLLs in IPv6 networks there is a need for a method of NDP mediation. However, since IPv6 nodes can have multiple IP addresses per AC interface, also referred to herein as IPv6 interface addresses or simply interface addresses, simply adopting a similar method as that used for ARP mediation for IP interworking VLLs is not desirable. This is because such a method would require a large amount of signaling to communicate these multiple IP addresses over the LDP control link. Therefore, there is a need to provide a method of NDP mediation that does not require the communication of CE device IPv6 interface addresses over the LDP control link.